is very difficult to write.

People find it a pleasure to

read, however, which helps to account for the popularity of writers like Craig Thomas. The company he keeps -- the dozens of authors of fat espionage thrillers of the turn-and-turn-again variety -- forms a distinctive fraternity in the continuum of mystery/detective/spy/ thriller fiction. Thomas runs to thickness around the waist, to a bit of sag in the middle of his thrillers, for he is now popular enough that his publisher obviously wants big books, long books, from him. There was a time when Thomas was more succinct, in Wolfsbane (still his best book) and Firefox. Now he is being Ludlumized, a process rather like blowing into a balloon, until each scene is a few pages longer than necessary, each conversation just a wee bit windy. It's too bad, and one hopes that Thomas might learn from the taciturn Clint Eastwood, who rockets through the sky in the motion picture version of Firefox, Thomas's greatest success, how to keep the words to the minimum. For the secret of narrative drive is economy: it's not killing two guards when one will do, not allowing the Russian informant to faint just at the moment he may name the Master Spy, especially when he faints three times. The principle of parsimony is essential to a good thriller.

Thomas writes far better than Ludlum. He often achieves the economy of words of Adam Hall. He can muster up some of the dulled irony of John le Carr,e. He knows how to make a chase scene drive the reader from page to page, in freezing mist, through the railway yards of Vienna, into the computer annexes of Hradcany Castle, across the broken hills of Afghanistan, fleeing from napalm: he is only a step behind Geoffrey Household at this kind of thing. Best of all, he gets his geography right: if his hero flees from the Prater Park, down across the train lines, and up onto Lassellestrasse, he will come to the Nord-bahnhof. Its good to read prose that has a sense of place and even better when the places are authentic: London, Helsinki, Prague -- Thomas has either been there or has a remarkable set of maps. Perhaps it ought not to matter that most thriller writers wind up a chase scene by sending a car right when they mean left, so that as they hurry toward the lakeside in Geneva they would, were their prose part of real life, actually be ascending the mountains behind. Thomas even gets his Viennese one-way system right, and that's a relief.

Though presented as if complex, the story of Lion's Run is actually quite simple. Sir Kenneth Aubrey, the director-general of British Intelligence, has been declared a traitor, the KGB having woven its web so cleverly that he cannot possibly prove his innocence for himself. Sir Kenneth's successor, Sir Andrew Babbington, could challenge the evidence if he wishes to, but apparently he shares the conviction that Sir Kenneth is guilty. Only Patrick Hyde, Sir Kenneth's bodyguard, an Australian with a limited vocabulary of expletives and a penchant for foreign languages, might be able to stay out of the net, find out the truth, save Sir Kenneth. So off Hyde is set running, with a variety of heavies, usually in a Mercedes, thin beams of light piercing the fog- bound gloom, close behind. Hyde will discover who the master traitor is, will break into the computer room, master the program, by which he can tap Moscow Centre, will in the end triumph. The plot is, then, a tissue of clich,es, and yet it works.

WHY DO plots like this one work? Partially because we, the readers, will them to. We want the formulae to work no less than a young mother needs to be able to count on pabulum. Because the formula is familiar in outline though fresh in execution, in its details. Because we suspect all will come out right in the end. Because there is something moodily romantic about racing across Europe, running for our lives: there are all those movies, Eric Ambler and Graham Greene, Claire Bloom and Richard Burton, Harry Lime and the heavy car, covered with snow, silently approaching from behind, running on its parking lights. We have seen it before, read it before, liked it then, like it now. And in Lion's Run, Craig Thomas demonstrates that he can provide the bits of analysis necessary to any narrative without slowing the flow. We know almost from the outset who the archtraitor really is, so that all of Thomas' writing talents, which are considerable, and all of our concentration can be directed to the chase, to the run itself. There is no heavy stuff here, no introspection about East and West, no Freud, Deconstructionism, or plot twist intended solely for effect: the run is straight, honest writing, what one might call simply a damn good read.